[180] These terms are explained on p. [115].
[181] Cf. Korotneff, Embryol. der Gryllotalpa. Zeits. f. wiss. Zool. (1885).
[182] In Gryllotalpa (Dohrn), as in Spiders, some Myriopods and Peripatus (Moseley, Phil. Trans., 1874), each stigma, with its branches, constitutes throughout life a separate system. The salivary glands arise in the same way, not, like the salivary glands of Vertebrates, as extensions of the alimentary canal, but as independent pits opening behind the mouth. Both the tracheal and the salivary passages are believed to be special modifications of cutaneous glands (Moseley).
[183] Loc. cit.
[184] This arrangement persists only in Ephemeridæ among Insects (Palmen, Ueb. paarigen Ausführungsgänge der Geschlechtsorgane bei Insekten, 1884).
[185] Genital pouch of the preceding description.
[186] Indications, which we have not found time to work out, lead us to think that the development of the specially modified segments and appendages in the male and female Cockroach needs re-examination. We hope to treat this subject separately on a future occasion.—L. C. M. and A. D.
[187] It may be useful to point out the following examples of parental care among animals in which, as a rule, the eggs are left to take care of themselves. It will be found that in general this instinct is associated with high zoological rank (best exemplified by Mammals and Birds), land or freshwater habitat, reduced number of eggs, and direct development.
Amphibia.—The eggs are sometimes hatched by the male (Alytes obstetricans, Rhinoderma Darwinii), or placed by the male in pouches on the back of the female (Pipa dorsigera, Notodelphis ovifera, Nototrema marsupiatum), or carried during hatching by the female (Polypedates reticulatus).
Fishes.—The Stickleback and others build nests. Of eleven genera of nest-building Fishes, eight are freshwater. The number of eggs is unusually small. Many Siluroids have the eggs hatched in the mouth of the males, a few under the belly of the female. The species are both marine and freshwater, the eggs few and large. Lophobranchiate fishes usually have the eggs hatched by the male. They are marine; the eggs few and large. Many sharks hatch their eggs, which are very few, within the body. Mustelus lævis has a placenta formed out of the yolk-sac.